Historically, the American approach to wildfire has been to try to suppress it whenever and wherever it appears. This strategy is often traced to the great fires of 1910. That year, massive blazes across the West burned millions of acres and killed dozens of firefighters. Smoke drifted as far as New England, along with tales of tragedy and devastation. Gifford Pinchot, first director of the nascent U.S. Forest Service, was convinced that fire threatened the economic well-being of the nation, and as the man in charge of a huge, federally owned empire of forested land, he was in a position to turn his ideas into policy. He began a campaign to banish fire.

"We understand that forest fires are wholly within the control of man," he declared.

Under Pinchot and his successors, firefighting became a courageous struggle. We grew adept at killing fires, especially small ones. But we did not understand that fire, like rain, is necessary. Those firefighting campaigns, combined with a decline in logging and a growing conservation movement, meant vegetation—potential fuel—began to pile up. A study published in 2005 reflects the sort of change seen across the West. Researchers at Northern Arizona University studying two patches of Arizona forest estimated that in the late 1800s they contained about 50 trees for every 2.5 acres. After nearly a century without fire, up to 1,700 trees now crowd the same area.

By stamping out small fires and allowing fuel to stockpile, our policies ensured that when conditions were right, fire would return—bigger, hotter, more destructive than ever. And the right conditions could become routine. Most climate models now strongly suggest that the recent drought is not just a temporary phenomenon but part of a long-term drying trend made worse by global warming. There comes a point where no amount of money, no measure of heroism, is enough. Far from "wholly within the control of man," fire becomes unstoppable.

Idaho's Lucky fire represents the American firefighting world in miniature. Crews from all over the West and beyond have come to fight it and a few other fires nearby. They work dawn to dusk, sleeping in tents or on bare ground. Helicopters costing up to $80,000 a day rattle overhead, dropping water and blood-red fire retardant. In a command tent far from the fire, the bill is tallied. By July 26, nine days after the fire began, it was $1.5 million. July 29: $2.6 million. August 1: $4.5 million. Dozens of fires burn elsewhere in Idaho alone.